Temps in Dallas have been around 37-40c, but depending on where you live you'll probably be used to it. The humidity is worse though. Hubbard's not far from Dallas. About an hour and a half. Dallas doesn't do much in the way of public transportation so a car might be the best idea. It's been a long time since I rented one, but I think it's around $25 a day or so.
Scottish Mag is right about Cabela's being better for hunters, Bass Pro is more fishing focused. The prices are good, but the selection (especially the ammo) is weak. Besides there are a ton of local shops that can get you set up just as well.